1. Field of the Invention
This invention relates to projectile firing weapons which use common engine fuels and an externally compressed air supply comprising a two,state (liquid/gas) propellant system, where liquid fuel is initially ignited in one volume which causes a separate air volume to compress, allowing extremely rapid combustion when another liquid fuel injection occurs in this second volume, further resulting in rapid expansion to fire the projectile.
2. Prior Art
The classic method of accelerating a projectile for firing is accomplished using solid chemical charges with ignition primers. Typically, either these solid charges are contained in casings and capped with the projectile, or the projectile, solid propellant charge, and the primer are individually loaded into the weapon.
The disadvantages of solid propellant systems are numerous. First, the primer, casings and charge occupy a volume at least equal to, and up to three times, that of the projectile. Thus, the space and volume requirements for the solid propellant system are limiting. Correspondingly, the weight of the solid propellant components present limitations.
Next, the lack of charge adjustability presents another limitation. The solid chemical propellants can be varied only by tedious, time-consuming methods, if this is even an option, thus removing this desirable feature from rapid-fire weapons. Similarly, combustion rates are an inherent physical property of solid propellants. Thus, adjustments to minimize muzzle flash and maximize the projectile velocity for the specific characteristics and firing conditions of the individual weapons are not readily obtainable.
Additionally, another disadvantage for solid chemical propellants is their potential hazardous effects, particularly in the combat environment. Since the solid propellants are highly combustive and/or explosive in nature, the presence of these items constitutes an extreme hazard from accidental or combat fire.
Moreover, another disadvantage for solid propellants in a combat environment is the muzzle flash and smoke upon firing. Burning fillers and uncombusted or partially combusted propellant, all typical of solid propellants systems, result in the discharge of incandescent and opaque particulate. The negative result is the significantly large, undesirable muzzle flash and smoke cloud that potentially may act as beacon to enemy troops and hinder the operator's field of vision.
Finally, solid propellant systems present disadvantages of logistics and cost.
Prior art also includes weapons which fire caseless ammunition with specially formulated liquid propellants. In applications such as described in McArthur U.S. Pat. Nos. 2,391,636 and Bulman 4,852,458, the projectile is first accelerated mechanically or via a separate propellant system prior to acceleration by the main chemical propellants.
Other prior art, such as that disclosed in Hoffman U.S. Pat No. 4,100,836, uses an externally powered piston in conjunction with specially formulated fuels to propel the projectile. The Patent of Jaqua, U.S. Pat. No. 4,281,582, discloses a two component liquid propellant, consisting of a fuel and a reacting oxidizer, which both are simultaneously injected into the combustion chamber using a differential area injection piston. Similarly, another liquid propellant gun, Mayer U.S. Pat. No. 4,341,147, again uses differential pistons to inject liquid propellant into the combustion chamber, but it has the advantage of controlling the continuous injection rate during firing by comprising a plurality of coaxial pistons. The patent of Magoon et al., U.S. Pat. No. 4,745,841, discloses the gun using liquid propellant and a differential piston to provide regenerative injection of the propellant into the combustion chamber after an initial ignition of propellant in the combustion chamber.
The disclosure of Nelson, U.S. Pat. No. 3,380,345, shows an engine weapon in which pressurized air in conjunction with distillate fuel oils are used for firing the projectiles. This invention attempts to achieve the pressurized air charge internally. Also, the weapon is spring powered. The fuel ignition in this gun is achieved through an electrical spark. Moreover, Nelson's design has no means to power the final stage of air compression into the combustion chamber. The Nelson invention employs a split clamshell breech/loading mechanism compared to a chambered, rotating cylinder assembly.